1. Field of the Invention
The invention relates to an implantable device for treatment of tinnitus which includes an electronic signal generation unit and a power source for power supply of the device.
2. Discussion of Related Art
Many individuals suffer from intermittent or permanent tinnitus which cannot be cured by surgery. Also, to date, there have been no approved drug forms of treatment for tinnitus. However, so-called tinnitus maskers are known, such as disclosed in published PCT application 90/07251. These maskers are small, battery-operated devices which are worn like a hearing aid behind or in the ear and cover (mask) the tinnitus psychoacoustically by artificial sounds which are emitted, for example, via a hearing aid speaker into the auditory canal and which reduce the disturbing tinnitus as far as possible below the threshold of perception. The artificial sounds are often narrowband noise (for example, third octave noise) which in its spectral position and its loudness level can be adjusted via a programming device to enable the maximum possible adaptation to the individual tinnitus situation.
Moreover, recently the so-called "retraining method" has been provided according to which, by combination of a metal training program and presentation of broadband sound (noise) near the hearing threshold, the perceptibility of the tinnitus is supposed to be largely suppressed (see the journal "Hoerakustik" 2/97, pages 26 and 27).
In the two aforementioned methods, technical devices similar to hearing aids can be visibly carried externally on the body in the area of the ear. As a result, these devices stigmatize the wearer and therefore are not willingly worn.
Furthermore, there are currently partially and fully implantable hearing aids for rehabilitation of inner ear impairment such as disclosed in published European patent application Nos. 0 499 940, and 0 831 674, U.S. Pat. Nos. 5,279,292; 5,498,226; 5,624,376; and 5,795,287. In fully implantable systems, the system is not visible, so that in addition to the advantages of high sound quality and the open auditory canal, high acceptance can be assumed.
U.S. Pat. No. 5,795,287 describes an implantable tinnitus masker with direct drive of the middle ear, for example via an electromechanical transducer which is coupled to the ossicle chain. This directly coupled transducer can preferably be a so-called "floating mass transducer" (FMT). This FMT corresponds to the transducer for implantable hearing aids described in U.S. Pat. No. 5,624,376. U.S. Pat. No. 5,795,287 clearly describes the concept of "direct drive" which is explicitly defined as drives including only the types of couplings to the inner ear for purposes of tinnitus masking which are of a mechanical nature. For example, direct drive couplings include direct mechanical converter couplings to one ossicle of the middle ear, such as for example by the FMT converter, and also air gap-coupled electromagnetic converters, such as for example described by Maniglia in U.S. Pat. No. 5,015,225.
All these electromechanical coupling types have the fundamental and serious disadvantage that the surgery for implantation of the entire masker system, or even only the electromechanical transducer, requires fundamentally mechanical manipulations on the ossicle chain of the middle ear or directly at the entry area of the inner ear (oval or round window) and thus involve a considerable risk of inner ear impairment. Furthermore, the necessary surgical opening of an sufficiently large access to the middle ear from the mastoid, for example in the area of the chorda facialis angle (med: "dorsal tympanotomy", as is necessary in the application of the FMT, can also involve the serious risk of facialis damage and the associated partial paralysis of the face. Furthermore, it cannot always be guaranteed that mechanical coupling will be of a long term, stable nature or that additional clinical damage will not occur, for example, pressure necroses in the area of the middle ear ossicle.